sync: GU retry with less explicit TimeTicks logic

sync/sessions/nudge_tracker.h

Index: sync/sessions/nudge_tracker.h
diff --git a/sync/sessions/nudge_tracker.h b/sync/sessions/nudge_tracker.h
index 1663f0ccad82b4d60af4626bb18a289a90c64bc7..276e8fa8f479c6f6bcc8968bb7f902ee4c58c8b2 100644
--- a/sync/sessions/nudge_tracker.h
+++ b/sync/sessions/nudge_tracker.h
@@ -36,14 +36,17 @@ class SYNC_EXPORT_PRIVATE NudgeTracker {
 
   // Returns true if there is a good reason for performing a get updates
   // request as part of the next sync cycle.
-  bool IsGetUpdatesRequired(base::TimeTicks now) const;
+  bool IsGetUpdatesRequired() const;
 
   // Return true if should perform a sync cycle for GU retry.
-  bool IsRetryRequired(base::TimeTicks now) const;
+  //
+  // This is sensitive to changes in 'current time'.  Make sure you're aware of
+  // any nearby calls to ToggleRetryFlagIfRequired().
+  bool IsRetryRequired() const;
 
   // Tells this class that all required update fetching or committing has
   // completed successfully.
-  void RecordSuccessfulSyncCycle(base::TimeTicks now);
+  void RecordSuccessfulSyncCycle();
 
   // Takes note of a local change.
   void RecordLocalChange(ModelTypeSet types);
@@ -105,12 +108,18 @@ class SYNC_EXPORT_PRIVATE NudgeTracker {
       ModelType type,
       sync_pb::DataTypeProgressMarker* progress) const;
 
+  // Flips the flag if we're due for a retry.
+  void ToggleRetryFlagIfRequired(base::TimeTicks now);
+
   // Adjusts the number of hints that can be stored locally.
   void SetHintBufferSize(size_t size);
 
-  void set_next_retry_time(base::TimeTicks next_retry_time) {
-    next_retry_time_ = next_retry_time;
-  }
+  // Schedules a retry GetUpdate request for some time in the future.
+  //
+  // The effects of this change are not guaranteed to take effect until
+  // ToggleRetryFlagIfRequired() is called.  That function should be called
+  // rarely (ie. only before a sync cycle, never during).
+  void SetNextRetryTime(base::TimeTicks next_retry_time);
 
  private:
   typedef std::map<ModelType, DataTypeTracker> TypeTrackerMap;
@@ -139,9 +148,13 @@ class SYNC_EXPORT_PRIVATE NudgeTracker {
 
   base::TimeTicks last_successful_sync_time_;
 
-  // A retry GU should be issued after this time.
+  // Time when the next retry is scheduled to execute.  Will be null if no
+  // retry is currently pending, or the is_retry_required flag is set.
   base::TimeTicks next_retry_time_;
 
+  // Set to true when the nudge tracker believes we're due for a GU retry.
+  bool is_retry_required_;
+
   DISALLOW_COPY_AND_ASSIGN(NudgeTracker);
 };